Flexible, planar, double sided air breathing microscale fuel cell

ABSTRACT

Flexible air-breathing microscale fuel cells are produced using ion exchange polymer membranes without silicon substrates or other rigid components. The microscale fuel cells provide long-life energy supply sources in portable electronics due to reduced volume, high energy density, and low cost. More particularly, the microscale fuel cell has a direct hydrogen flow-through porous anode electrode with a pair of air-breathing cathodes.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. ProvisionalApplication No. 62/422,820, filed Nov. 16, 2016 and entitled FLEXIBLE,PLANAR, DOUBLE SIDED AIR BREATHING MICROSCALE FUEL CELL, whichprovisional application, including its specification, abstract anddrawings, is incorporated herein by reference in its entriety.

FIELD OF THE INVENTION

The present invention relates to fuel cells and, more particularly, tomicro-sized fuel cells that are flexible, planar, double sided, and airbreathing, which are suitable for use as miniaturized energy sources.Throughout the present application, the terms “miniature,” “microscale,”“micro,” and “small” are used interchangeably to refer to the very smallscale of the fuel cells being discussed herein, i.e., less than aboutone millimeter in thickness.

BACKGROUND OF THE INVENTION

Clean, efficient and environmentally-friendly miniaturized energysources remain one of the major challenges for improving electronicdevices. Due to the spread of more compact and thinner portableelectronic systems, miniaturization of micro power sources is asimportant as ever. The scaling down of energy sources promises highervolumetric efficiency, however, new designs and manufacturing processesare also required as a result. These new approaches are needed in orderto meet the challenges of integrating system components without complexand bulky packaging which detract from the ultimate objectives of smallsystem size and light weight.

Microscale fuel cells have been attracting much attention as leadingcandidates for prospective portable power sources and batteryreplacements as they benefit from large energy density, high efficiency,immediate recharging and inherent non-polluting characteristic. Buildinga microscale fuel cell that takes advantage of a microfluidic conceptpromises a highly efficient energy generator with increasedsurface-to-volume ratio within the fuel cell. Such micro fuel celldesigns have the potential to satisfy the accelerating power generationdemands in mobile applications. The success of microelectromechanical(hereinafter “MEMS”) technology in making cheaper and more efficientproducts has created new pathways for micro fuel cell advancement.

Much effort in fuel cell miniaturization is focused on techniques basedon silicon wafers because they are the most common substrate in MEMStechnology. The combination of silicon-based devices with polymeric fuelcells at low scale can lead to inappropriate structural and materialsadjustments. Polymeric materials and especially polydimethylsiloxane(hereinafter “PDMS”) have been proposed to make micro fuel cellcomponents due to their rapid and adaptable fabrication methods,however, the assembly of these materials typically needs a glass orother rigid substrate which compromises volumetric efficiency, andsealing still remains a challenge.

SUMMARY OF THE INVENTION

The present invention relates to flexible air-breathing microscale fuelcells having ion-exchange polymer membranes, without silicon substrates,as well as a direct hydrogen flow-through porous anode electrode with apair of air-breathing cathodes. The microscale fuel cells providelong-life energy sources in portable electronics with reduced volume,high energy density, and low cost.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, reference ismade to the following detailed description of an exemplary embodimentconsidered in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic cross-sectional diagram showing the components ofan exemplary embodiment of a microscale fuel cell and its operation;

FIG. 2 is a schematic exploded diagram showing the components of themicroscale fuel cell of FIG. 1;

FIGS. 3A-3E show the steps of a method for production of a patterned ionexchange polymer membrane suitable for use in an exemplary embodiment ofthe microscale fuel cell;

FIG. 4 is a schematic diagram showing an exemplary method for sealingion exchange polymer membranes around an anode;

FIGS. 5A and 5B are schematic drawings showing an alternative exemplarymethod for sealing ion exchange membranes around an anode andsimultaneously forming microchannels;

FIG. 6 is a microscopic top view of an inlet microchannel and an inletin fluid (i.e., liquid or gas) communication with an anode chamber;

FIG. 7 is a graph showing the open circuit voltage over time for asample microscale fuel cell produced in accordance with the methodsdescribed herein;

FIG. 8 is a graph showing the power density for various currentdensities at various hydrogen flow rates for a sample microscale fuelcell produced in accordance with the methods described herein;

FIG. 9 is a microscopic top view of a microchannel produced by thesealing method shown in FIG. 4; and

FIG. 10 is a microscopic top view of a microchannel produced by thesealing method shown in FIGS. 5A and 5B.

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT

The present disclosure provides a novel microscale microfluidic fuelcell of the proton exchange membrane (hereinafter “PEM”) type, in whichthe micro flow channels, for fuel and oxidant input, and the membraneelectrode assembly (hereinafter “MEA”) are fabricated on a flat andflexible ion exchange polymer membrane without any other substrate.Suitable ion exchange polymer membrane materials include, for examplewithout limitation, fluorinated polymers or co-polymers. Suchfluorinated polymers and copolymers are commercially available, forexample, under the tradename Fumatech BWT GMBh located in St. Ingbert,Germany, and under the tradename NAFION, from The Chemours Companylocated in Wilmington, Del., U.S.A., and under the tradename FLEMIONfrom AGC Chemicals America located in Exton, Pa., U.S.A. Sulfonatedpolymers and copolymers are good proton conductors suitable for use inPEM fuel cells, as well as having excellent thermal and mechanicalstability.

Making a microscale fuel cell on ion exchange polymer membranes providesthe ability for considerable scaling down of the size of fuel cellpackaging in two or three dimensions, while maintaining high poweroutput. One major challenge of this method is cost-effective deeppatterning of the ion exchange polymer membrane at small scale toproduce patterned substrates having features of the required height ordepth without damaging the characteristics of the membrane. Deeppatterning creates small, high-resolution structures or patterns in thesurface of a substrate, such as an ion exchange polymer membrane.Lacking the proper height or depth in the microfluidic structure posesthe risk of the need to increase the fuel/oxidant running pressure, inwhich the costs of process control, energy expenditure, and the sealingof the microfluidic device also become more challenging.

Prior art PEM fuel cells (not shown) typically consist of a planarstacking of the membrane, electrocatalyst layers, carbon paper gasdiffusion media, graphite flow field, and gold-plated metal currentcollectors. The thickness of a single stack assembly is severalcentimeters in size and significantly scales-up for a multi-stackassembly. Conversely, for the thin, microscale fuel cells describedherein, a planar flexible stack can be constructed having less than amillimeter of thickness. The use of fewer materials, particularly theexclusion of the graphite flow field that accounts for greater than 50%of the fuel cell's weight, makes the designed microscale fuel cell ahigh energy density device.

The microscale fuel cell (pFC) described and disclosed herein is anair-breathing flexible device that is constructed out of ion exchangepolymer membranes. Thermally sealed microchannels structured within theion exchange polymer membranes make it possible for the microchannels todeliver the gas/fuel to the microchamber area and to discharge theexcess reactants and/or byproducts. Alternatively, preventing dischargeflow allows the device to operate in “dead-end” mode, in which the fuelis essentially completely reacted and no discharge from the anode areais required.

With reference to FIGS. 1 and 2, in an exemplary embodiment, themicroscale fuel cell 10 generally includes first and second generallyplanar, porous air-breathing cathodes 12, 14 with a shared anode 16between them. The microscale fuel cell 10 can be considered an ordinarypower source like a battery, whereby it is connected to any type ofelectrical load such as the lightbulb shown in FIG. 1.

The cathodes 12, 14 and anode 16 are known devices and may be made fromcarbon-based mesh, paper or cloth and infused or coated with a metalcatalyst, such as but not limited to platinum, or another precious ornon-precious metal, alone or in combination. By way of example only, thecathodes 12, 14 can be in the shape of a square having 5.0 mm sides,while the anode 16 can also be in the shape of a square having 4.0 mmsides.

As shown in FIGS. 1 and 2, interposed between the first cathode 12 andthe anode 16 is a first ion exchange polymer membrane 18 and interposedbetween the second cathode 14 and the anode 16 is a second ion exchangepolymer membrane 20. The ion exchange polymer membranes 18, 20 aretypically sealed around the anode 16. In that regard, and by way ofexample only, the ion exchange polymer membranes 18, 20 can be in theshape of a rectangle having a width of 10.0 mm and a length of 20.0 mm.In an alternate embodiment, either the first cathode 12 or the secondcathode 14 can be eliminated, whereby the resulting microscale fuel cellwould comprise a single cathode, a single anode and a pair of ionexchange polymer membranes. Furthermore, the microscale fuel cell 10includes at least one microchannel, such as the inlet and outletmicrochannels 22, 24 shown in FIGS. 1 and 2. The inlet microchannel 22is in fluid (i.e., liquid or gas) communication with the anode 16 andwith an inlet opening 26 for the inlet (i.e., delivery) of reactionfluids (e.g., hydrogen). Similarly, the outlet microchannel 24 is influid (i.e., liquid or gas) communication with the anode 16 and anoutlet opening 28, for the outlet (i.e., discharge) of reaction fluids(e.g., unreacted hydrogen and water vapor). The microchannels 22, 24,inlet opening 26, and outlet opening 28 are all patterned onto the ionexchange polymer membranes 18, 20 either by lithography processes orother processes known to persons of ordinary skill in the art (e.g.,imprinting, embossing, etching and deposition). By way of example only,the microchannels 22, 24 can have a width of 0.4 mm, while the inletopening 26 and the outlet opening 28 can have a radius of 1.5 mm.

The gas flow fields and current collectors (not shown per se) areintegrated into the first and second porous air-breathing cathodes 12,14. The sealing process employed to form the microscale fuel cell 10,which will be described below, also binds the microfluidic reactionchamber formed by the first and second ion exchange polymer membranes18, 20 to porous media (i.e., the first and second porous air-breathingcathodes 12, 14), which creates a “flow-through porous” design for themicroscale fuel cell 10. Also, the fabrication technique employed may beused to manufacture three-dimensional microchannel structures withvarying thicknesses on arbitrary polymeric substrates.

In operation, ambient air (shown by curved arrows in FIG. 1) enters themicroscale fuel cell 10 through the first and second porousair-breathing cathodes 12, 14. Hydrogen (shown by arrow H₂) enters themicroscale fuel cell 10 through the inlet opening 26 and inletmicrochannel 22, through which the hydrogen travels to the anode 16. Thedouble-sided air breathing microscale fuel cell 10 produces electricalpower that is generated from the reduction and oxidation half reactionsoccurring at the cathode and anode electrodes (which are integrated intothe cathodes 12, 14 and anode 16 and, therefore, are not shown per se).Hydrogen or a small alcohol, such as for example, methanol, can be fedto the anode 16 as fuel, while oxygen passes through the cathodes 12, 14to the anode 16. The anode oxidation reaction results in the productionof protons and electrons. The protons are transported through the ionexchange polymer membranes 18, 20 to the cathodes 12, 14 on the top andbottom surfaces of the microscale fuel cell 10, while the electrons areconducted through electrical wires 30, 32 (see FIG. 1), doing work bypowering the connected load (e.g., the lightbulb shown in FIG. 1).

In the present microscale fuel cell 10, the energy density has beenincreased using two air breathing cathodes 12, 14 sharing a common anode16 to maximize the cathode interface to the ambient air, while thesystem components are stacked in parallel on a common anode 16 tofurther improve the energy density. The air-breathing cathodes 12, 14are able to react passively with the oxygen from ambient air. Usingair-breathing cathodes 12, 14 reduces the size, noise, costs andsimplifies system requirements since oxygen inlet is fully passive. Alsobased on the advantages of the scaling laws and microfluidicenvironment, miniaturization promises reduced chemical consumption,safety, high surface-area-to-volume ratios, and improved control overmass and heat transfer superior to macroscopic reaction devices. In thisrespect, the microscale fuel cell 10 was miniaturized to improve itsperformance as a power generating device.

In the method disclosed and described herein, a hot embossing method isemployed for patterning the ion exchange polymer membranes to fabricatemicrochannels. Hot embossing is a technique or method whereby asubstrate or sheet of material, such as a polymer, is heated to atemperature at which it softens and can be made to flow easily. In thisstate, it is impressed with a stamp or master (created from a differentmaterial, such as a metal, which stays rigid under these conditions),which is a negative of the pattern that is to be created in the heatedsubstrate material. The stamp is then withdrawn, leaving the desiredpattern in the heated substrate material which hardens as it cools. Thestamp can be reused, depending on the materials it is made from and theforces required for the embossing step. Hence a single stamp may, inprinciple, be used and reused to create many replicates of the patternedsubstrate.

Silicon (Si) is a common material to be used as the stamp for use in ahot embossing process since it can be patterned reliably by knownfabrication processes. However, deep etching to create the required Sistamp is costly. In addition, such a Si stamp is prone to cleavageduring hot pressing. Therefore, in exemplary embodiments of themicroscale fuel cell described herein, another material such asstainless steel or other metal may be used to form the stamp.Alternatively, materials such as a photoresist or a metal such asnickel, can be layered on the Si substrate to make the stamp. Suitablephotoresist materials include, for example without limitation, a thickepoxy-based negative photoresist. One such suitable epoxy-based negativephotoresist material is commercially available under the tradename SU-8from MicroChem Corporation, Newton, Mass., U.S.A. Further, it has beenfound that microscale patterning of ion exchange polymer membranes withan epoxy-based negative photoresist stamp is feasible without anysurfactant coating, which is commonly required to assist in release ofthe stamp from the substrate. In addition, after imprinting orpatterning the ion exchange polymer membrane, the patterned epoxy-basednegative photoresist material can be placed on a new substrate andreused, which makes the epoxy-based negative photoresist a low-coststamp option.

A process will now be described, in conjunction with FIGS. 3A-3E, forfabrication of a stamp 40 comprising a patterned epoxy-based negativephotoresist material 42 a on a Si substrate 44 and using that stamp 40to pattern an ion exchange polymer membrane 46. First, a thick layer ofepoxy-based negative photoresist material 42 is spin-coated onto asubstrate 44 comprising Si and soft baked (see FIG. 3A). The epoxy-basednegative photoresist material 42 is then patterned by photolithographyor a similar technology. For example, although not shown per se in thefigures, the epoxy-based negative photoresist material layer 42 may beexposed to UV light through a photomask to produce a pattern on theepoxy-based negative photoresist material layer 42. After such UVexposure, a two-step bake process may be employed to crosslink the stamp40. The stamp 40 may then be subjected to a development process wherebysoluble material is removed from the epoxy-based negative photoresistmaterial layer 42. After development, the patterned epoxy-based negativephotoresist stamp 42 a may be hard baked to enhance its rigidity at hightemperature. The foregoing techniques produce the stamp 40 shownschematically in FIG. 3B comprising the patterned epoxy-based negativephotoresist material layer 42 a on a Si substrate 44.

With reference now to FIGS. 3C to 3E, using the stamp 40 to pattern anuntreated ion exchange polymer membrane 46 will now be described. Moreparticularly, the untreated ion exchange polymer membrane 46 issandwiched between the stamp 40 and a second substrate layer 48, whichmay also comprise Si and having same dimensions as the stamp 40 (seeFIG. 3C). The sandwiched layers (not shown per se) are then placed intoa suitable embossing apparatus (not shown) for hot embossing at atemperature of from about 170° C. to about 200° C., a pressure of fromabout 120 pounds per square inch (psi) to about 180 psi, for a period oftime of from about 2 to about 5 minutes. During hot embossing, thepattern on the patterned epoxy-based negative photoresist material layer42 a is impressed into the ion exchange polymer membrane 46 to form apatterned ion exchange polymer material membrane 46 a (see FIG. 3D). Theembossed layers are removed from the apparatus and separated manuallyfrom the two Si substrates 44, 48, leaving the patterned epoxy-basednegative resist 42 a embedded in the patterned ion exchange polymermembrane 46 a. The patterned ion exchange polymer membrane 46 a may bereleased from the patterned epoxy-based negative photoresist 42 a (seeFIG. 3E) by simply bending the flexible patterned ion exchange polymermembrane 46 a.

FIG. 4 is a schematic representation showing a portion of the processfor making a microscale fuel cell 10 in accordance with the descriptionprovided herein. More particularly, using a thermal sealing process, theanode 16 is sealed in between the patterned ion exchange polymermembrane 46 a (as described above) and a second ion exchange polymermembrane 52, which may be patterned or untreated. For example, a thermalsealing process which involves gas-cushion hot pressing (as shown byarrows in FIG. 4) may be employed. In some embodiments, the thermalsealing process is performed at a temperature of from about 220° C. toabout 250° C., a pressure of from about 100 psi to about 150 psi, for aperiod of time of from about 2 to about 5 minutes.

In some embodiments, the second ion exchange polymer membrane 52 may bemade of a different ion exchange polymer material and in otherembodiments both membranes 46 a, 52 may be made of the same type of ionexchange polymer material. For example, the second ion exchange polymermembrane may be made of a higher power density ion exchange polymermaterial. Using the patterned ion exchange polymer membrane 46 a resultsin a microscale fuel cell 10 having microchannels (not shown) defined bythose in the pattern on the ion exchange polymer membrane 46a. FIG. 6,for example, shows a microscopic photograph of a microchannel 22, 24 andcorresponding inlet or outlet opening 26, 28 in communication with amicrochamber 60 in which the anode 16 is positioned.

Thus, a process for production of a microscale fuel cell where apatterned ion exchange polymer membrane is employed would include thefollowing steps:

1. Hot embossing molds are fabricated from epoxy-based negativephotoresist by photolithography on a Si substrate.

2. Patterning of the ion exchange polymer membrane is performed in agas-cushion pressure chamber, intended for a uniform pressuredistribution and unvarying microchannel depths, by hot embossing theprepared mold onto the ion exchange polymer membrane.

3. The electrocatalyst layer is coated on the cut carbon papers for theanode and cathode electrodes with appropriate catalyst loading.

4. In the thermal sealing step, another ion exchange polymer membranecovers the entire patterned ion exchange polymer membrane and thesemembranes are sealed around the anode by gas-cushion hot pressing.

FIGS. 5A-5B provide a schematic representation of a portion of adifferent process for making a microscale fuel cell 10 in accordancewith the description provided herein. More particularly, this differentprocess does not use a patterned ion exchange polymer membrane, butrather, two untreated ion exchange polymer membranes 54, 56 are layeredon either side of the anode 16 and sealed around the anode 16, again bya thermal sealing process such as gas-cushion hot pressing under theconditions described above. In such embodiments, the untreated ionexchange polymer membranes 54, 56 may be made of the same or differention exchange polymer materials. For example, one or both of theuntreated ion exchange polymer membranes 54, 56 may be made of higherpower density ion exchange polymer material when this process isemployed.

FIG. 5B schematically shows the procedure to fabricate microchannels inthe sealing process which does not employ a patterned ion exchangepolymer membrane. A copper wire 58 may be employed as a mold positionedin between the ion exchange polymer membranes 54, 56 to formmicrochannels during the gas-cushioned hot embossing procedure. Afterhot embossing, the copper wire 58 can be drawn out of the microchannels(not shown) through the inlet and outlet openings (not shown).

In the microscale fuel cell described herein, endplates were eliminatedby incorporating porous carbon papers both for current collecting andgas flow fields. This results in very compact designs, while bringing inthe unique advantages of a “flow through” porous media instead of a moreconventional “flow-over” porous electrode design. The forced convectionthrough the electrodes avoids flooding and gas diffusion limitations,thereby extending the linear region of the cell potential versus currentdensity plot and hence improving the cell performance.

Regarding the power product of the microscale fuel cell, although higherpower densities are accessible in supported cells/stacks with planarconfigurations, our flexible micro fuel cell can deliver highervolumetric power density (i.e., approximately 437 milliWatts per squarecentimeter (mW/cm³)) than its reported air-breathing counterparts. Thisperformance gap may be further enhanced when considering gravimetricpower densities. Moreover, the very thin device is promising fortwo-dimensional stacking.

EXAMPLES

Sample microscale fuel cells were prepared by both sealing methodsdescribed above, i.e., one using a patterned ion exchange membrane andanother using only untreated ion exchange polymer membranes.

A stamp having SU-8 on a Si substrate was fabricated and then used topattern a NAFION® membrane. First, a thick layer of SU-8-2100photoresist (MicroChem Corporation, Newton, Mass., USA) was spin-coated,soft baked and exposed to UV light through a photomask. After exposure,a two-step bake was employed to crosslink the polymer. Afterdevelopment, the patterned SU-8 micro stamps were hard baked to enhancetheir rigidity at high temperature. Untreated Nafion 1110 membranes weresandwiched between the stamp and a Si substrate with the same dimensionsas the stamp. The sandwiched samples were then hot embossed at 190° C.and 160 psi for 5 min. The embossed samples were separated from the twoSi substrates manually, leaving the SU-8 mold in the Nafion. The sampleswere released from the SU-8 mold by simply bending the membranes.

Anodes were sealed between ion exchange polymer membranes according toboth methods described above in connection with FIGS. 4 and 5A-5B. Inthe sealing step for the method shown in FIG. 4, a 212 Nafion sheetcovered the entire patterned Nafion 1110 substrate by gas-cushion hotpressing. The thermal sealing was done at 220° C. and 130 psi withoutany Si substrate involved for both methods. FIG. 9 shows a micrograph ofa microchannel formed by the aforesaid method.

In the method shown in FIGS. 5A-5B, the porous carbon electrode wasemployed as the mold for the sealing step. In other words, for themethod shown in FIGS. 5A-5B the microlithography process for patterningthe thick Nafion film was eliminated and it was then possible to use thehigher power density 212 Nafion for both ion exchange polymer membraneson both sides of the microscale fuel cell. The procedure illustrated inFIG. 5B was used to fabricate the microchannels. More particularly, acopper wire was employed as a mold to form the microchannels in agas-cushioned hot embossing chamber. After hot embossing, the copperwires were drawn out through the inlet and outlet openings. FIG. 10shows a micrograph of a microchannel formed by the aforesaid sealingmethod using the copper wire to form the microchannels.

In accordance with the arrangement shown in FIG. 2, the microscale fuelcell consisted of five layers. The mask design embossed into thepatterned ion exchange polymer membrane included two 400 micron-widthmicrochannels to connect the gas inlet and outlet openings to a 0.5×0.5cm² anode chamber in the middle of the device. The anode chamber wasfilled with a porous carbon paper screen printed with a catalyst layeron both sides. FIG. 6 is a microscopic top-view of the inletmicrochannel connecting the inlet opening to the anode microchamber.

The performance of the assembled microscale fuel cell was assessed atroom temperature, hydrogen delivery at atmospheric pressure (no backpressure), and ambient air pressure on the cathode surfaces. Tostabilize the performance results at different flow conditions,electrical testing was preceded by a dry hydrogen conditioning period at10 standard cubic centimeters per minute (sccm) and 0.6 Volt for twohours. For performance testing, H₂ was fed from 10 sccm to 40 sccm tothe anode m icrocham ber.

FIG. 7 shows the open circuit voltage (OCV) of the microscale fuel cellversus time for a feed rate of 10 sccm H₂ fuel. After applying hydrogen,the OCV increased at a slow speed followed by a rapid rise to a maximumof 0.97 V and remained nearly constant after that. FIG. 8 shows thepower density curves for a flexible microscale fuel cell operated atdifferent hydrogen flow rates in ambient conditions. As shown,increasing the flow rate generally improved the performance and themaximum power density increased with increase in the flow rate. At 10sccm hydrogen flow rate, the maximum power density was about 22 mWcm⁻³¹² and it increased significantly with an increase in flow rate to 20sccm. A minor improvement in maximum power density (27.6 to 34.2 mWcm⁻²)was observed by increasing the hydrogen flow rate from 20 to 40 sccm.

While at least one exemplary embodiment has been presented in theforegoing detailed description, it should be appreciated that variousadditional embodiments and modifications are possible that remain withinthe intent and function of the invention described and contemplatedherein. It should also be appreciated that the exemplary embodiment orembodiments are merely examples, and are not intended to limit thescope, applicability, or configuration of the invention in any way. Theforegoing detailed description provides those skilled in the art with aconvenient road map for implementing an exemplary embodiment of theinvention, it being understood that various changes may be made in thefunction and arrangement of elements described in an exemplaryembodiment without departing from the scope of the invention as setforth in the appended claims and their legal equivalents.

We claim:
 1. A flexible micro-scale fuel cell, comprising: a porousanode; a first air-breathing cathode positioned to one side of saidanode; a first ion exchange polymer membrane positioned between saidanode and said first air-breathing cathode; a second ion exchangepolymer membrane positioned to an opposite side of said anode; firstmeans in fluid communication with said anode for delivering reactionfluids to said anode; and second means in fluid communication with saidanode for discharging reaction fluids from said anode.
 2. The flexiblemicro-scale fuel cell of claim 1, wherein said first and second ionexchange polymer membranes cooperate to create a seal around said anode.3. The flexible micro-scale fuel cell of claim 1, wherein said firstmeans includes a first microchannel provided in at least one of saidfirst and second ion exchange polymer membranes and said second meansincludes a second microchannel provided in at least one of said firstand second ion exchange polymer membranes.
 4. The flexible micro-scalefuel cell of claim 3, wherein said first means further includes an inletopening in fluid communication with said first microchannel and saidsecond means further includes an outlet opening in fluid communicationwith said second microchannel.
 5. The flexible micro-scale fuel cell ofclaim 4, wherein said inlet opening is provided in at least one of saidfirst and second ion exchange polymer membranes and said outlet openingis provided in at least one of said first and second ion exchangepolymer membranes.
 6. The flexible micro-scale fuel cell of claim 5,wherein said first and second microchannels are provided in said firstand second ion exchange polymer membranes.
 7. The flexible micro-scalefuel cell of claim 6, wherein said inlet opening is provided in saidfirst and second ion exchange polymer membranes.
 8. The flexiblemicro-scale fuel cell of claim 7, wherein said outlet opening isprovided in said first and second ion exchange polymer membranes.
 9. Theflexible micro-scale fuel cell of claim 3, wherein said first and secondmicrochannels and said inlet and outlet openings are patterned onto atleast one of said first and second ion exchange polymer membranes. 10.The flexible micro-scale fuel cell of claim 9, wherein said first andsecond microchannels and said inlet and outlet openings are patternedonto said first and second ion exchange polymer membranes.
 11. Theflexible micro-scale fuel cell of claim 1, wherein said first and secondion exchange polymer membranes are made from the same material.
 12. Theflexible micro-scale fuel cell of claim 1, wherein said first and secondion exchange polymer membranes are made from different materials. 13.The flexible micro-scale fuel cell of claim 12, wherein said first ionexchange polymer membrane is made from a first material having a firstpower density and said second ion exchange polymer membrane is made froma second material having a second power density which is higher thansaid first power density.
 14. The flexible micro-scale fuel cell ofclaim 1, wherein said first and second ion exchange polymer membranesare flat and flexible.
 15. The flexible micro-scale fuel cell of claim14, wherein said first and second ion exchange polymer membranes aremade from fluorinated polymers or co-polymers.
 16. The flexiblemicro-scale fuel cell of claim 1, wherein said fuel cell is of theproton exchange membrane type.
 17. The flexible micro-scale fuel cell ofclaim 1, wherein said first and second means are arranged on oppositeends of said anode, whereby reaction fluids flow directly through saidanode between said opposite ends thereof.
 18. The flexible micro-scalefuel cell of claim 1, further comprising a second air-breathing cathodepositioned to said opposite side of said anode such that said second ionexchange polymer membrane is positioned between said anode and saidsecond air-breathing cathode.
 19. A method of making a flexiblemicro-scale fuel cell, comprises the steps of: providing a porous anode;arranging a first air-breathing cathode to one side of said anode;interposing a first ion exchange polymer membrane between said anode andsaid first air-breathing cathode; arranging a second ion exchangepolymer membrane to an opposite side of said anode; providing at leastone of said first and second ion exchange polymer membranes with a firstmicrochannel such that said first microchannel is in fluid communicationwith said anode at one end thereof; and providing at least one of saidfirst and second ion exchange polymer membranes with a secondmicrochannel such that said second microchannel is in fluidcommunication with said anode at an opposite end thereof.
 20. The methodof claim 19, further comprising the steps of providing at least one ofsaid first and second ion exchange polymer membranes with an inletopening such that said inlet opening is in fluid communication with saidfirst microchannel and providing at least one of said first and secondion exchange polymer membranes with an outlet opening such that saidoutlet opening is in fluid communication with said second m icrochannel.